The Standard Behind Every Frame
NZS 3604 — Timber-Framed Buildings — is the primary standard governing light timber frame construction in New Zealand. It sets out the requirements for framing members (sizes, species, grades), connections (nailing, bolting, strapping), bracing (wind and earthquake resistance), and the conditions under which the standard applies. If you’re framing a house in New Zealand and the job doesn’t have a specific engineer’s design, you’re working to NZS 3604.
Understanding NZS 3604 — not just following the drawings, but understanding what the standard is trying to achieve and why specific requirements exist — makes you a better framer and helps you identify when something is wrong before it’s covered up by linings.
Timber Species and Grades
NZS 3604 specifies the timber grades acceptable for different framing applications. The standard uses Visual Grade (VG) and Machine Grade (MSG) classifications, and sets minimum requirements for structural framing members in terms of grade. Radiata pine — the dominant framing timber in New Zealand — is typically supplied as MSG8 for structural framing. Using subgrade timber in structural applications is a Building Code compliance failure that can affect both structural performance and consent sign-off.
Bracing: The Critical System
Bracing is the framing system’s resistance to horizontal loads — wind and earthquake. NZS 3604 specifies bracing demand (how much bracing a building needs) and bracing capacity (how much different bracing systems provide). The balance between demand and capacity, in both directions of the building, must be achieved on every level of the building. Getting bracing wrong — insufficient bracing, wrong panel lengths, incorrect nailing — is a structural failure that affects the building’s ability to perform in a wind or earthquake event.
Connections and Fixings
NZS 3604’s connection requirements — the nailing schedules, strapping details, and hold-down fixings that tie the framing together and anchor it to the foundation — are specific and mandatory. The nailing schedule in NZS 3604 specifies not just the number of nails but their size, type, and position for each framing connection. Using the wrong nails, or under-nailing, produces connections with less capacity than the standard assumes — reducing structural performance without any visible indication of the problem.